Cells, Tissues, Organs, Organ Systems and Organism Body Organization Cells, Tissues, Organs, Organ Systems and Organism
Level One: Cells A cell is a basic unit of structure and function in a living thing. The human body contains about 100 trillion cells. Cells can not be seen without a microscope. Three important structures to recall are cell membrane, nucleus, and cytoplasm. What is the function of the nucleus?
Functions of Cell Structures Cell membrane: forms the outside boundary of the cell; materials move across the cell’s membranes Nucleus: the control center that directs the cell’s activities and contains information that determines the cell’s characteristics Cytoplasm: a clear, jellylike substance in which many important cell structures are found
Level Two: Tissues A tissue is a group of similar cells that perform the same function. The human body contains 4 basic types of tissue: muscle tissue nerve tissue connective tissue epithelial tissue
Muscle Tissue Like the muscle cells that form it, muscle tissue can contract or shorten. One kind of muscle tissue allows the body to move. Other kinds of muscle tissue move: 1. blood through the heart 2. food through the digestive system
Nerve Tissue Nerve tissue directs and controls movement. Nerve tissue carries messages back and forth between the brain and every other part of the body. Nerve tissue enables you to see, hear, and think. Your brain, spinal cord and nerves consist of nerve tissue. Under a microscope you can see the neurons & glial cells.
Epithelial Tissue Epithelial tissue covers the surfaces of your body and the outside of your internal organs. Under a microscope epithelial tissue looks like it is packed tight together & in sheets or layers. Your skin is composed of 2 layers of epithelial tissue, the epidermis and dermis. It is also composed of connective, nerve & muscle tissue.
Connective Tissue Connective tissue provides support for your body and connects all its parts. Examples of connective tissue are: bones & tendons-for support fat-provides insulation from cold & stores energy blood-travels to all parts of your body Under a microscope connective tissue looks like fibrous strands of protein collagen
Organs An organ is a structure that is composed of different kinds of tissue. It performs a specific job. For example, the heart pumps blood throughout the body An interesting fact about the heart: it contains all 4 kinds of tissue! So does the skin!
Organ Systems An organ system is a group of organs that work together to perform a major function. 11 systems make up the human body: Circulatory 7. Nervous Digestive 8. Reproductive Endocrine 9. Respiratory Excretory 10. Skeletal Immune 11. Integumentary (Skin) Muscular
Thinking Critically Answer the following questions: What systems of the body are involved when you prepare a sandwich and then eat it? Which 2 systems work together to get oxygen to your cells?